2020年职称英语考试《理工类》考试共65题，分为单选题和多选题和判断题和计算题和简答题和不定项。小编每天为您准备了5道每日一练题目（附答案解析），一步一步陪你备考，每一次练习的成功，都会淋漓尽致的反映在分数上。一起加油前行。

1、Radiocarbon Dating
Nowadays scientists can answer many questions about the past through a technique called radiocarbon (放射性碳), or carbon - 14 dating. One key to understanding how and why something happened is to discover when it happened.
Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at the University of Chicago. An atom of ordinary carbon, called carbon -12, has six protons (质子) and six neutrons (中子) in its nucleus (原子核). Carbon - 14, or C - 14, is a radioactive, unstable form of carbon that has two extra neutrons. It returns to a more stable form of carbon through a process called decay (衰减). This process involves the loss of the extra neutrons and energy from the nucleus.
In Libby's radiocarbon dating technique, the weak radioactive emissions(放射)from this decay process are counted by instruments such as a radiation detector and counter. The decay rate is used to determine the proportion of C -14 atoms in the sample being dated.
Carbon - 14 is produced in the Earth's atmosphere when nitrogen(氮) - 14, or N - 14, interacts with cosmic rays (宇宙射线). Scientists believe since the Earth was formed, the amount of nitrogen in the atmosphere has remained constant. Consequently, C -14 formation is thought to occur at a constant rate. Now the ratio of C -14 to other carbon atoms in the atmosphere is known. Most scientists agree that this ratio is useful for dating items back to at least 50,000 years.
All life on Earth is made of organic molecules (分子) that contain carbon atoms coming from the atmosphere. So all living things have about the same ratio of C -14 atoms to other carbon atoms in their tissues (组织). Once an organism (有机体) dies it stops taking in carbon in any form, and the C -14 already present begins to decay. Over time the amount of C - 14 in the material decreases and the ratio of C - 14 to other carbon atoms goes down. In terms of radiocarbon dating, the fewer C -14 atoms in a sample, the older that sample is.
Radar is used to determine the characteristics of radiocarbon.【单选题】

A.Right

B.Wrong

C.Not mentioned

正确答案:C

答案解析:本题有较大难度，答案依据不明显，需要通读全文作出判断。通读全文后可以发现文章并未提及使用雷达来进行放射性碳测定，所以本题是未提及的，答案是C。

2、While serving in the Senate in the early 1970s Barbara Jordan supported legislation to ban discrimination and to deal with environment problems. 【单选题】

A.list

B.forbid

C.handle

D.investigate

正确答案:B

答案解析:forbid和ban都表示“禁止、不准、不许”；handle:拿、处理、应付、控制；investigate：调查。

3、His shoes were shined to perfection.【单选题】

A.cleared

B.polished

C.washed

D.mended

正确答案:B

答案解析:他的鞋被擦得铮亮。本题难度不大，干扰项干扰不明显。查词典，找到shine的引申意思“擦亮”，选项里只有polish有擦亮鞋的意思，所以确定答案不难，本题是送分题。

4、Cell Phones
1. Believe it or not, cell phones have been around for over a quarter of a century. The first commercial cell phone system was developed by the Japanese in 1979, but cell phones have changed a lot since that time. The early cell phones were big and heavy but they have developed into small and light palm sized models. There are huge developments in their functions, too. We have had call forwarding, text messaging, answering services and hands - free use for years, but now there are new facilities, such as instant access to the Internet and receiving and sending photos.
2. Cell phones have become very common in our lives. Recent statistics suggest one in three people on the planet now have cell phone, and most of them say they couldn't live without one, Cell phones are used in every area of our lives and have become a necessary tool, used for essential arrangements, social contact and business. It easier to call for help on the highway. It possible to keep in touch with people "on the move" when people are traveling.
3. Cell phones have made communication easier and have reduced the need for family arguments f We can use cell phones to let our family know we'll be late or if there's a sudden change of plan or an emergency. Cell phones have eased the worries of millions of parents when their teenagers are out late. They can now contact their children at any time.
4. This does not mean that cell phones are all good news. Cell phones have brought with them a number of new headaches for their owners. It costs a lot to replace stolen phones, It is becoming a frequent occurrence, and have you ever seen such a huge phone bills? More serious, however, Cell phones bring the potential health problem. There are fears that radiation from the phones may cause brain tumor(肿瘤). This may be a time bomb waiting to happen to younger people who have grown up with cell phones. They simply can't live without cell phones!
Paragraph 5 ______
【单选题】

A.Cell phones and the family

B.Commercial cell phone systems

C.Cell phones in everyday life

D.Cell phones for teenagers

E.History of cell phones

F.Problems with cell phones

正确答案:F

答案解析:本题难度不大，主旨句比较明显，就是第四段的第一句：这并不意味着手机带来的都是好消息。后面谈到了手机带来的问题，F项Problems with cell phones是本段主旨句的近义解释，是答案。

5、An Intelligent Car
Driving needs sharp eyes, keen ears, quick brain, and coordination between hands and the brain. Many human drivers have all. these and can control a fast-moving car. But how does an intelligent car control itself ?
There is a virtual driver in the smart car. This virtual driver has "eyes," "brains", "hands" and "feet", too. The mini-cameras on each side of the car are his "eyes," which observe the road and conditions ahead of it. They watch the traffic to the car's left and right. There is also a highly automatic driving system in the car. It is the built-in computer, which is the virtual driver's "brain". His "brain" calculates the speeds of other moving cars near it and analyzes their positions. Basing on this information, it chooses the right line for the intelligent cars, and gives instructions to the "hands" and "feets" to act accordingly. In this way, the virtual driver controls his car.
What is the virtual driver's best advantage? He reacts rapidly. The mini-cameras are sending images continuously to the "brain". It completes the processing of the images within 100 milliseconds. However, the world's best driver at least needs one second to react. ______, when he takes action, he needs one more second.
The virtual driver is really wonderful. He can reduce the accident rate. considerably on expressway. In this case, can we let him have the wheel at any time and in any place? Experts warn that we cannot do that just yet. His ability to recognize things is still limited. He can now only drive an intelligent car on expressways.
【单选题】

A.So

B.However

C.Besides

D.Therefore

正确答案:C

答案解析:因为前一句已经是however引导的表示“转折关系”的句子，因此不可能接着又出现however引导的另一转折句，所以首先排除B。空白位于句首，而且有一个逗号与句子其他部分隔开，因此空白处应该出现逻辑副词。选项A和D在用做逻辑副词的用法和词义上接近，相互排除，因此答案为C。从空白所在句子的句意上看，该句引出另一信息，因此从句意上判断也需要besides引出表示递进关系的句子。